U.S. patent number 10,580,543 [Application Number 15/967,720] was granted by the patent office on 2020-03-03 for neutron sealed source.
This patent grant is currently assigned to QSA GLOBAL, INC.. The grantee listed for this patent is Illinois Tool Works Inc.. Invention is credited to Mark Vose.
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United States Patent |
10,580,543 |
Vose |
March 3, 2020 |
Neutron sealed source
Abstract
A neutron sealed source holds cermet wire sources, such as
Californium-252/Palladium wires, in separate blind apertures within
a stainless steel block. The stainless steel block is part of an
inner encapsulation and includes blind apertures arranged in
rotational symmetry for receiving the cermet wire sources. The
cermet wire sources are separated from each other and the fission
and decay heat is rejected through the stainless steel block.
Inventors: |
Vose; Mark (Windham, NH) |
Applicant: |
Name |
City |
State |
Country |
Type |
Illinois Tool Works Inc. |
Glenview |
IL |
US |
|
|
Assignee: |
QSA GLOBAL, INC. (Burlington,
MA)
|
Family
ID: |
67953841 |
Appl.
No.: |
15/967,720 |
Filed: |
May 1, 2018 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20190341163 A1 |
Nov 7, 2019 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G21F
5/10 (20130101); G21G 4/06 (20130101); G21G
4/02 (20130101); G21C 7/34 (20130101) |
Current International
Class: |
G21G
4/02 (20060101); G21G 4/06 (20060101); G21F
5/10 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Y A Karelin et al., "Californium-252 Neutron Sources", Applied
Radiation and Isotopes, Elsevier, Oxford GB, vol. 48, No. 10-12,
Oct. 12, 1997, pp. 1563-1566. cited by applicant .
International Search report issued in PCT/US/2019/023813 dated Oct.
25, 2019. cited by applicant.
|
Primary Examiner: Stoffa; Wyatt A
Attorney, Agent or Firm: McCarter & English, LLP
Claims
What is claimed is:
1. A neutron source, including: a first capsule structure, having a
cylindrical shape and including a cylindrical block structure
defined by first outer walls, the first outer walls extending
beyond the block structure and defining a first open end providing
access to the block structure, the block structure forming a first
closed end; and the block structure including a plurality of
cylindrical blind apertures for receiving a respective plurality of
active sources, wherein the apertures are parallel to each other,
separated from each other, and co-extensive; a second capsule
structure encapsulating the first capsule structure; wherein the
first outer wall extending beyond the block structure forms a first
seat within the first outer wall and adjacent to the block
structure; wherein the first seat receives a first lid which is
welded or otherwise sealed to an interior of the first outer wall
in a position immediately adjacent to the block structure and
openings of the apertures; wherein the second capsule structure
includes second outer walls, a second open end and a second closed
end, the second outer walls being concentrically outward from the
first outer walls; and wherein the first open end of first capsule
structure abuts an interior of the second closed end of the second
capsule structure and the first closed end of the first capsule
structure is inwardly adjacent from the second open end of the
second capsule structure thereby forming a second seat.
2. The neutron source of claim 1 wherein the second seat receives a
second lid which is welded or otherwise sealed to an interior of
the second outer wall in a position immediately adjacent to the
first closed end of the first capsule structure.
3. The neutron source of claim 1 wherein the first capsule
structure is formed from stainless steel.
4. The neutron source of claim 1 wherein the second capsule
structure is formed from a material chosen from the group
consisting of stainless steel, titanium, nickel and zirconium.
5. The neutron source of claim 1 further including a plurality of
active sources emitting neutrons, wherein an active source is
placed into each aperture of said plurality of apertures.
6. The neutron source of claim 5 wherein the active sources include
Californium-252.
7. The neutron source of claim 6 wherein the active sources further
include palladium.
8. The neutron source of claim 5 wherein the active sources include
Californium-252 in the form of Pd/Cf.sub.2O.sub.3
(palladium/californium (III) oxide).
9. The neutron source of claim 7 wherein the active sources are
configured as lengths of cermet wire.
10. A neutron source, including: a first capsule structure
including a block structure defined by first outer walls, the first
outer walls extending beyond the block structure and defining a
first open end providing access to the block structure, the block
structure forming a first closed end; the block structure including
a plurality of compartments for receiving a respective plurality of
active sources, the compartments separated by heat sink walls; a
second capsule structure, encapsulating the first capsule
structure; wherein the first outer wall extending beyond the block
structure forms a first seat within the first outer wall and
adjacent to the block structure; wherein the first seat receives a
first lid which is welded or otherwise sealed to an interior of the
first outer wall in a position immediately adjacent to the block
structure and openings of the compartments; wherein the second
capsule structure includes second outer walls, a second open end
and a second closed end, the second outer walls being
concentrically outward from the first outer walls; and wherein the
first open end of first capsule structure abuts an interior of the
second closed end of the second capsule structure and the first
closed end of the first capsule structure is inwardly adjacent from
the second open end of the second capsule structure thereby forming
a second seat.
11. The neutron source of claim 10 wherein the first capsule
structure is formed a material chosen from the group consisting of
stainless steel, titanium, nickel and zirconium.
12. The neutron source of claim 10 wherein the second seat receives
a second lid which is welded or otherwise sealed to an interior of
the second outer wall in a position immediately adjacent to the
first closed end of the first capsule structure.
13. The neutron source of claim 10 wherein the second capsule
structure is formed from a material chosen from the group
consisting of stainless steel, titanium, nickel and zirconium.
Description
BACKGROUND OF THE DISCLOSURE
Field of the Disclosure
The present disclosure relates to a neutron sealed source which
holds cermet wire sources, such as Californium-252/Palladium wires,
in separate blind apertures within a stainless steel block, thereby
rejecting internally generated fission and decay heat from the
cermet wire sources through the stainless steel block.
Description of the Prior Art
In the prior art, it is known to use Californium-252 as a neutron
source to provide stable initiation of the nuclear chain reaction
during the start up of nuclear reactors. This provides for a more
predictable, safe and reliable start up than relying solely on
spontaneous fission or delayed fission within the reactor fuel
rods. Such a neutron source increases the neutron flux and thereby
the fission reaction rate in the reactor thereby allowing the
reactor to be initially started even in an otherwise subcritical
state. Additionally, such a known neutron source within the reactor
during start up allows for the testing of neutron flux detectors.
In the prior art, a plurality of cermet wires comprising
Californium-252 and Palladium are loosely placed inside a single
source cavity and then the source capsule is welded shut, as shown
in FIGS. 1 and 2. These source capsules are typically placed
throughout the reactor core. However, in such a configuration, the
cermet Wires may touch each other. Such a configuration may result
in heat from both fission and decay which is high enough to melt
the cermet wires during operation within a nuclear reactor thereby
risking capsule integrity.
OBJECTS AND SUMMARY OF THE DISCLOSURE
It is therefore an object of the present disclosure to provide a
neutron source, using Californium-252 or similar isotopes, which
can reject the heat generated in the neutron source during
operation in a nuclear reactor, from both fission and decay, and
avoid or minimize melting of the source which would risk capsule
integrity.
This and other objects are attained by providing a neutron sealed
source wherein a stainless steel block, insert, or similar
structure is provided with a plurality of compartments or blind
apertures, each for receiving a length of Californium-252/Palladium
cermet wire or other neutron source. A typical embodiment would
include four such compartments or blind apertures, but it is
envisioned that more or less compartments or blind apertures may be
used for various applications. The stainless steel block, or
similar structure, after receiving the plurality of lengths of
Californium-252/Palladium cermet wire or other neutron source, is
welded or otherwise sealed within a capsule structure.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objects and advantages of the disclosure will become
apparent from the following description and from the accompanying
drawings, wherein:
FIG. 1 is a side cut-away view of a typical neutron source of the
prior art.
FIG. 2 is an end cut-away view of a typical neutron source of the
prior art.
FIG. 3 is a side cut-away view of an embodiment of the sealed
neutron source of the present application.
FIG. 4 is an end cut-away view of an embodiment of the sealed
neutron source of the present application.
FIG. 5 is an end view of the integrated insert of an embodiment of
the sealed neutron source of the present application.
FIG. 6 is a cross-sectional view along plane 6-6 of FIG. 5.
FIG. 7 is an end view of the capsule assembly of an embodiment of
the sealed neutron source of the present application.
FIG. 8 is a cross-sectional view along plane 8-8 of FIG. 7.
FIG. 9 is a plan view of the lid of an embodiment of the sealed
neutron source of the present application.
FIG. 10 is a cross-sectional vies along plane 10-10 of FIG. 9.
FIG. 11 is a perspective view of the lid of an embodiment of the
sealed neutron source of the present application.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings in detail, wherein like numerals
indicate like elements through the several views, one sees that an
embodiment of the sealed neutron source 10 of the present
disclosure is illustrated in FIGS. 3-10. The encapsulation in an
exemplary embodiment may be firmed from stainless steel bar, type
304L, condition A (annealed), hot or cold finished, UNS 30403,
whereas the active source is typically formed from cermet wires
(formed by compacting and sintering a metal and a ceramic)
containing Californium-252/Palladium in the chemical form of
Pd/Cf.sub.2O.sub.3 (Californium (III) oxide). Those skilled in the
art will recognize a range of equivalents. In particular,
alternative materials for the encapsulation are nickel, titanium
and zirconium.
As shown in FIGS. 3-6, the sealed neutron source 10 includes inner
integrated cylindrical insert 12 with a relatively solid
cylindrical block portion 14 with a closed external end 15. The
cylindrical walls 16 of cylindrical block portion 14 extend past
cylindrical block portion 14 thereby forming hollow cylindrical lid
seat portion 18 adjacent to the cylindrical block portion 14 and
further forming open end 19. The exterior portion of cylindrical
walls 16 adjacent to open end 19 may include a circumferential
chamfered portion 21 of slightly reduced diameter. The inner
integrated cylindrical insert 12 thereby forms a first or inner
capsule structure. As best shown in FIGS. 5 and 6, four blind
apertures 20, 22, 24, 26 are bored or otherwise formed in
cylindrical block portion 14 at rotationally symmetric locations
(that is, in the case of four blind apertures, spaced ninety
degrees apart rotationally, as shown in FIG. 5). The blind
apertures 20, 22, 24, 26 are typically parallel with each other,
and co-extensive with each other (i.e., longitudinally aligned with
each other and of equal depth). The blind apertures 20, 22, 24, 26
form compartments which are separated from each other by the
material of the cylindrical block portion 14.
As shown in FIGS. 3 and 4, in the fully assembled configuration,
active sources, such as cermet wires 200, typically of
Californium-252/Palladium (in the form Pd/Cf.sub.2O.sub.3), are
placed within the blind apertures 20, 22, 24, 26. The cermet wires
200 are prevented from touching each other by the material of
cylindrical block portion 14. Additionally, during operation, the
cylindrical block portion 14 serves as a heat sink for fission heat
and decay heat from the cermet wires 200. The material of
cylindrical block portion 14, as best illustrated in FIG. 4, acts
as a separator for the cermet wires 200 within the apertures or
compartments 20, 22, 24, 26 as well as a heat sink. Typical
dimensions of the cermet wires 200 are a length of 8.85 millimeters
and a nominal diameter of 1.22-1.27 millimeters. Cermet wires 200
may have a slightly oval cross section and may have a typical
activity loading of 20 milligrams per millimeter. Dimensions for an
embodiment of the blind apertures 20, 22, 24, 26 are a total depth
of 11.5 millimeters and a nominal diameter of 1.65 millimeters.
Dimensions for an embodiment of the inner integrated cylindrical
insert 12 are 14.20 millimeters in length and 6.0 millimeters in
diameter. However, those skilled in the art will recognize that
other dimensions may be preferable for different applications.
As shown in FIGS. 7 and 8, an internal lid 30 includes a transverse
circular plate-like portion 32 with longitudinal extending walls 34
extending around the periphery thereof for welding or otherwise
sealing against the interior of cylindrical walls 16 when
positioned or seated within hollow cylindrical lid seat portion 18
adjacent to the cylindrical block portion 14, after insertion of
the cermet wires 200 into apertures 20, 22, 24, 26.
As shown in FIG. 3, the outer cylindrical capsule 40 includes outer
cylindrical walls 42 with an open end 44 and a closed end 46. The
outer cylindrical capsule 40 forms a second or outer capsule
structure, which is concentrically outward from the inner
integrated cylindrical insert 12. The exterior portion of
cylindrical walls 42 adjacent to open end 44 may include a
circumferential chamfered portion 45 of slightly reduced diameter.
The inner integrated cylindrical insert 12, including the cermet
wires 200 and the internal lid 30, is inserted into the open end 44
of outer cylindrical capsule 40 so that internal lid 30 is urged
against the closed end 46 of the outer cylindrical capsule 40. The
closed external end 15 of solid cylindrical block portion 14 is
positioned inwardly adjacent from the open end 44 of outer
cylindrical capsule 40, thereby providing a cylindrical space or
seat to receive outer lid 50 which is welded or otherwise scaled in
place with respect to the interior of the outer cylindrical walls
42 inwardly adjacent from open end 44 and adjacent to closed
external end 15 of inner integrated cylindrical insert 12, Outer
lid 50 includes a transverse circular plate-like portion 52 with
longitudinal extending walls 54 extending around the periphery
thereof for engaging against the interior of outer cylindrical
walls 42. Dimensions for an embodiment of the outer cylindrical
capsule 40 are 17.20 millimeters in length and 7.825 millimeters in
diameter. However, those skilled in the art, will recognize that
other dimensions may be preferable for different applications.
In operation, sealed neutron sources 10, typically surrounded by
cladding (typically, but not limited to, zirconium, not shown) and
configured as a start-up rod, are typically placed in regularly
spaced positions among the fuel rods of a nuclear reactor which is
being started up. In some applications, a mixture of ninety percent
helium and ten percent air may be placed between the cladding (not
shown) and the sealed neutron sources 10. The neutrons emanating
from the Californium-252 initiate or increase the fission chain
reaction within the fuel rods of the nuclear reactor.
Thus the several aforementioned objects and advantages are most
effectively attained. Although preferred embodiments of the
invention have been disclosed and described in detail herein, it
should be understood that this invention is in no sense limited
thereby.
* * * * *